1. Field of the Invention
The present invention relates to an image forming apparatus, such as a laser printer or the like.
2. Description of the Related Art
An image forming apparatus using electrophotography, such as a copier or a laser printer, has hitherto adopted a heat-roller-type fuser which transports a sheet material having an unfixed toner image formed thereon while heating the sheet material, to thus fix a toner image. In such an image forming apparatus, a curl arises during the course of the sheet material passing through the fuser, which may exert an adverse effect, such as deterioration of ease of stacking of sheet materials on an output tray. For this reason, as described in JP-A-9-188458 which will be described below, an image forming apparatus equipped with a curl elimination mechanism for straightening a curl of a sheet material has already been put into practice. This curl elimination mechanism is disposed downstream of the fuser and includes a curl-straightening roller to be rotationally driven and a pair of press rollers which oppose the curl-straightening roller and are rotationally driven so as to follow the curl-straightening roller. Grooves are formed in a circumferential direction in the outer peripheral surfaces of the respective press rollers. The sheet material is transported along an outer peripheral surface of the curl-straightening roller while being nipped between three rollers, whereby the sheet material is curled in a direction opposite that in which the sheet material has been curled by the fusing means, to thus eliminate the curl.